The phrase "assert in" is grammatically correct and can be used in written English.
One example of using "assert in" in a sentence could be: "The speaker boldly asserted in his speech that the new policies would benefit all citizens."
For example, look for new ways of setting terms of engagement that we each assert in our dealings online.
If Trump wants to argue he didn't commit the crimes, as he used to assert in April, fine.
The court's "intervention is necessary to preserve the integrity" of that decision, the Planned Parenthood lawyers assert in their petition.
The banks assert in the court filing that the limitations will hobble their defenses while unfairly letting the housing agency proceed with its case.
Humanistic tradition, rather than revolutionary inspiration, would lead Francis Bacon to assert in the early 17th century that the passions should become objects of systematic investigation.
He discerned structural parallels between Archaeopteryx and Deinonychus, leading him to assert in 1973 that birds had evolved from theropod dinosaurs, the group to which Deinonychus belonged.
Objectors assert in this Court, as they did in the District Court and Court of Appeals, an array of jurisdictional barriers.
As we assert in our article, "[t]he expansion of corporate space is a threat to both private and public space.
To be successful, MNCs will have to rethink every element of their business models, the authors assert in this seminal HBR article from 1998.
Sanchez and Sorcher, who work as day-care providers, assert in the lawsuit that they lack time to go to school to complete the required degrees.
